It is known to alkoxylate higher alcohols having 8-22 carbon atoms with ethylene oxide or propylene oxide or with mixtures of the two alkylene oxides and subsequently to convert the resulting alkoxylated product with diepoxides. Using such products it is possible to prepare aqueous solutions of a high viscosity. In DE 3134494, thickeners are made by single or plural reaction of an alcohol or a diol with ethylene oxide, propylene oxide or mixtures thereof and subsequent reaction with a diepoxide. In the examples of DE 3134494, the EO/PO mixtures are in a weight ratio of about 1:3 and the diepoxide used is vinylcyclohexane diepoxide (VCH). The preparation of such alkoxylated alcohols and their suitability as thickening agents are also disclosed in U.S. Pat. Nos. 3,538,033 and 4,102,795. U.S. Pat. No. 3,538,033 relates to thickeners obtained by reaction of aliphatic alcohols with ethylene oxide and subsequent reaction with a diepoxide such as limondiepoxide or VCH. The obtained products are solid and therefore difficult to handle. U.S. Pat. No. 4,102,795 discloses a fabric or hair softener containing a quaternary ammonium compound, water and a product obtained by reaction of an aliphatic alcohol with ethylene oxide, propylene oxide or mixtures thereof followed by reaction with a compound such as VCH.
The reaction of alcohols with ethylene oxide/propylene oxide mixtures leads to polyethers with different reactive terminal OH groups, with the ratio of primary OH groups to secondary OH groups being dependent on the reaction conditions. Since the composition of the later products formed by reaction of the alkoxylates with diepoxides is basically dependent on the type of hydroxyl terminal group of the alkoxylates, and variations in reaction conditions (e.g., temperature, EO/PO ratio) are unavoidable when preparing alkoxylates, it is difficult to prepare products of reproducible composition and quality.
Highly effective polyether-based thickening agents display in, e.g., water a great dependence of viscosity on temperature, which within the field of application of nonflammable hydraulic fluids presents a major drawback.
Therefore, there is still need for the preparation of a thickening agent that has reproducible properties, is universally suited to be used for the thickening of different water-based systems, and displays little viscosity-temperature dependence.